Brien Nolan, Dublin City University
GR17, the 17th International Conference on General Relativity and Gravitation, took place in the Royal Dublin Society convention centre, Dublin, Ireland from July 18th-23rd this summer. This conference series, held under the auspices of the International Society on General Relativity and Gravitation provides a forum for a triennial review of all areas of research in gravitation, as well as an opportunity to look forward to and plan for future challenges. This report can only give a very brief flavour of the content of the conference. The proceedings will be published next year by World Scientific and in the meantime, abstracts and links to some talks are available at the conference website (please note that will not be in operation from late 2004 on). The conference was attended by just under 700 scientific delegates.

The organization of the GRn conferences is in the hands of a Scientific Organizing Committee, whose principal remit is to select plenary speakers and workshop chairs, and a Local Organizing Committee who handle organizational aspects. For GR17 these were chaired by Curt Cutler (AEI, Golm) and Petros Florides (Trinity College Dublin) respectively.

The conference was opened on the morning of Monday 19th July by Her Excellency Mrs Mary McAleese, President of the Republic of Ireland, who delivered a well received address mentioning the contributions of John Lighton Synge to relativity and William Rowan Hamilton to physics generally. She also exhorted the audience to make the most of the week's opportunities to learn and discuss and to leave Dublin with a renewed commitment to their vocation as scientists. Petros Florides presented Mrs McAleese with copies of books by Stephen Hawking, Roger Penrose and Kip Thorne to mark the occasion, which prompted her to comment that she had never been given so much homework in her life. The opening also included the presentation by the (outgoing) Society president Bob Wald to Eanna Flanagan of the Xanthopoulous Award and a memorial lecture on JL Synge by Petros Florides. Ted Newman spoke briefly about the life and contribution to relativity of Peter Bergmann, who passed away since the last GR meeting.

There were 16 plenary lectures and 19 workshops at GR17. The former number represents a slight reduction on the number at GR16 held in Durban: this was done to allow more time for informal discussion. The 19 workshops were divided between afternoon parallel sessions and two evening poster sessions. The promise - and subsequent appearance - of a glass or two of wine during the poster sessions led to their being very well attended, with discussions only dying down as RDS staff began turning off the lights.

The SOC attracted an exceptional list of plenary speakers to GR17. The scientific content of the conference was initiated by Sterl Phinney (Caltech), who spoke about what we hope to learn about astrophysics and relativity from the LISA mission, as well as what subsequent missions may tell us about cosmology and the early universe. Piotr Chrusciel (Tours) gave a review of key results in Mathematical Relativity since GR16, focusing on global properties of the (vacuum) Einstein equations. Don Marolf spoke about the current status of the conjectured AdS/CFT correspondence of string theory, as well as its more controversial generalizations to other quantum theories of gravity.

Barry Barish (LIGO/Caltech) reviewed the status of the worldwide network of gravitational wave observatories and the scientific data currently being generated, and spoke about the prospects for the future of gravitational wave detection by this network. John Baez (UC Riverside) gave an expository talk on spin networks, spin foams and loop quantum gravity, highlighting the theory's successes in accounts of black hole entropy and the big bang. Miguel Alcubierre (Mexico City) had the unenviable task of reviewing recent progress in numerical relativity, both in terms of the theoretical framework (hyperbolic formulations, gauge choices, boundary conditions) and astrophysical simulations.

Wednesday morning saw the Gravity Research Funded session, chaired by Louis Witten. GRF provides funding for each GRn conference to invite speakers whose interests and expertise are in areas that are tangential to or slightly outside general relativity. Thus the audience at GR17 had the opportunity to hear Sir Martin Rees (Cambridge) speak about black holes in active galactic nuclei, Jim Peebles (Princeton) present a detailed critical review of the $\Lambda-$CDM cosmological tests and John Preskill (Caltech) introduce the theory of and prospects for quantum computing.

Preskill took to the stage again on Wednesday afternoon, when Stephen Hawking (Cambridge) presented his proposed solution of the black hole information paradox. Preskill jointly chaired the session with Kip Thorne, who is the third party to a bet (Thorne & Hawking vs. Preskill) on the issue. The event, introduced by Petros Florides, attracted a lot of media attention and so the scientific audience was joined by numerous members of the fourth estate to witness Hawking - but not Thorne - concede the bet and to watch Preskill wave his prize (an encyclopedia of baseball, from which information can be extracted at will) triumphantly over his head. (This correspondent was greatly amused by media reporting on the shenanigans, with references to an ``audience of Dublin boffins" being stunned by Hawking's confession that he ``got the hole thing wrong". GR17 was referred to as the ``brains Olympics" - in which case Preskill's parody of Olympian glory was spot on.)

Back at the science end of things, Eric Poisson (Guelph) spoke first on Thursday morning on the gravitational self-force (he began by asking where all the TV cameras had gone). Licia Verde (Pennsylvania) reviewed the implications for cosmology of the first year WMAP data, and promised that the second year data would be available "soon". Joseph Polchinski (UCSB) spoke about recent work that shows that certain superstrings populating the early universe could expand to cosmic scales today and be a significant source of gravitational waves.

The first of the Friday morning lectures was given by Lars Bildsten (KITP, UCSB), who spoke about recent advances in relativistic astrophysics (sensitive X-ray astronomy; solar black hole masses; data from PSR 0737-3039) and mentioned the consequent challenges for theorists and the gravitational wave detection community. Nergis Mavalvala (MIT) talked about the current status of advanced gravitational wave detector technology, and how this is now showing the way to a quantum-limited interferometer. The final plenary lecture was given by David Langlois (IAP, Paris) who reviewed the implications of the braneworld scenario for gravitation and cosmology. The focus was on the standard braneworld picture of our 4-d world resident in a 5-d bulk.

It is impossible to mention individually any of the large number of oral and poster presentations made in the workshops, but note that the conference book of abstracts is available online (see url above). Close to 600 (different) abstracts were submitted in all, amounting to some 400 talks and 200 posters. There were two public lectures held during the week. Kip Thorne spoke on Monday night about what we will learn from the new science of gravitational wave astronomy, and Roger Penrose spoke on Friday night, giving his personal opinions on some popular contemporary physical theories which he categorized under the headings ``Fashion, Faith and Fantasy". Other business during the week included the election of the new GRG Society officers; Cliff Will succeeds Bob Wald as president.

Astonishingly for Dublin, delegates encountered only one day of rain, allowing us to have lunch and coffee in the RDS grounds most days and enjoy what passes for good weather here. We look forward to even more sunshine at GR18 in Sydney in 2007.

Jorge Pullin 2004-09-10